U.S. military forces aboard Amphibious Assault Vehicles (AAV) manuevre on South China Sea near the shore of San Antonio, Zambales during the annual "Balikatan" (shoulder-to-shoulder) war games with Filipino soldiers in northern Philippines April 21, 2015.

Filipino activists denounced China's coast guard on Tuesday for turning water cannon on Philippine fishing boats in disputed waters, near where hundreds of Filipino and American Marines landed on a beach in a mock assault.

The presidential palace in Manila said China's coast guard used water cannon on Monday to drive away a group of Filipino fishermen at Scarborough Shoal, damaging some of their wooden boats. Chinese ships rammed a fishing boat in the area a few months back.

China in 2012 took control of Scarborough Shoal, about 130 miles west of a former U.S. naval base northwest of Manila, preventing Filipino fishermen from getting near the rich fishing grounds.

"China has no right to use water cannon on the poor fishermen," Renato Reyes, secretary-general of left-wing activist group Bayan (Nation), said in a statement, while criticising the government's dependence on the U.S. military to protect the country.

"To stand up to China, we need to develop our economy and our capacity for external defence. We can't do this by hanging on the coat tails of Uncle Sam," Reyes said.

China claims most of the potentially energy-rich South China Sea, with overlapping claims from the Philippines, Vietnam, Malaysia, Brunei and Taiwan, and denies charges its actions in what it says is its own territory are provocative. The Foreign Ministry has yet to comment on the latest accusations.

Philippine President Benigno Aquino has directed the Foreign Affairs and National Defence departments to come up with a response to the water cannon incident, said presidential spokeswoman Abigail Valte.

Philippine and U.S. Marines resumed their biggest combined military exercise in 15 years on Tuesday, a demonstration of Washington's commitment to its long-time ally as it rebalances to Asia in the face of China's expansion in the South China Sea.

Not far from Scarborough Shoal, about 750 Marines from the Philippines and United States landed on a beach in two waves using amphibious assault vehicles to retake an island in a mock battle during the largest drills in years in the country.

"This is an exercise," Colonel Doroteo Jose Jalandoni told journalists at a naval base in Zambales province. "We are not looking at other things. We just want to improve our skills and proficiency and test the two allies' ability to operate together."